Mahmoud Bek is obviously a title (Bek = Bey), one of the titles of nobility for Ottomans before. The first two words could be purely turkish though.
“zoor” could be also “Zevar” since the Waw letter (or W) was used by the ottomans (before changing into latin) as “V.”

Seems the writing is engraved on a protective ring of a trigger… logically seems to be indeed a turkish artifact.
However, the owner seems to be someone named Mahmoud Bek. The rest is left for any Turkish visitors to translate!

I’m Dan Newman, owner of the old gun. It’s an 1851 .36 caliber Navy Colt. I found the gun in a back alley antique store in Ankara, Turkey in 1983. The pistol itself is in pretty rough condition, but the grips, backstrap, and trigger guard make it unique. They are all of etched sliver. They were apparently added when it was new. The writing on the trigger guard is the old Turkish script, according to my Turkish buddy in Ankara. He also said that the gun had to have been owned by either a sultan or a highwayman, as those were the only two classes of Turkish people in the 1800s who could have afforded such an item. He’s likely right. I appreciate everyone’s efforts. If anyone would like more photos of the old gun, just write to me at danmnewman@comcast.net. The silver work on it is truly magnificent.

As a postscript: The title of respect “Bey” is still used in Turkey. It’s rather like using “Mr.” in the U.S. My name is Dan Newman, but when my Turkish employees wanted to address me formally, they called me “Dan Bey.” One of the ladies in my office was named Ender Ucuk. The formal address for her was “Ender Hanam” versus the masculine “Bey.”

Is the Hb zwr mHmwd bk the only text written there? I seem to see more text off to the right, coming before what we see clearly in the picture. At the top there seems to be a Taa’ and below it, possible a nuun, and I’m assuming this means there must be more text preceding what we see, off to the right of what the photo shows. If you could put up a picture of what’s on the other side, we might get a better idea of the whole inscription.

A note on Bek (Bey), it also appears in the name of the Uzbek people which appears to translate loosely as “free nobleman”.